Lipases have been extensively used in bioconversion of lipids to make high value products, for example sugar esters, for use in a wide range of industries, including the food and/or feed industries, the cosmetics and/or skin care industries, the oleochemical industry and the pharmaceutical industry.
When bioconversion processes require hydrolysis of lipid substrates, lipolytic enzymes can be used in high water environments. However, when bioconversion processes require interesterification or transesterification reactions such as by alcoholysis the use of lipases in high water environments can be detrimental due to unwanted hydrolysis reactions, which result in unwanted bioproducts and/or lower yields of the bioconversion product.
Typically, bioconversion processes requiring interesterification and/or transesterification have utilised lipases in non-water environments such as in oil systems and/or in organic solvent systems such as in butanol, methanol or hexane. Such systems provide an environment in which both the polar acceptor molecule and the lipid donor molecule can be at least partially solubilised, and the lipase has sufficient enzyme activity. Although a small amount of water is required for any enzymatic activity, the amount of water is strictly maintained at a low level to avoid hydrolytic activity of the enzyme.
Conventionally sugar esters, protein esters or hydroxyacid esters have been produced by chemical synthesis using inorganic catalysts. Convention bioconversion processes for the production of sugar esters or hydroxyacid esters utilise lipases in organic solvent environments or supercritical fluids where there is only a low amount of (if any) water present.
Lecointe et al Biotechnology Letters, Vol 18., No. 8 (August), pp 869-874 disclose a study of a number of lipase enzymes and their activity in an aqueous media on the production of methyl ester or butyl ester from methanol and butanol, respectively, Lecointe et al teach a lipase/acyltransferase from Candida parapsilosis which as methanol or butanol concentrations increased showed a reduced hydrolysis activity and an enhanced capability of the enzyme to produce methyl ester and butyl ester. The use of a lipase/acyltransferase from C. parapsilosis in the production of fatty hydroxamic acid is taught in Vaysse et al J. of Biotechnology 53 (1997) 41-46.
Lipase:cholesterol acyltransferases have been known for some time (see for example Buckley—Biochemistry 1983, 22, 5490-5493). In particular, glycerophospholipid:cholesterol acyl transferases (often referred to as GCATs) have been found, which like the plant and/or mammalian lecithin:cholesterol acyltransferases (LCATs), will catalyse fatty acid transfer between phosphatidylcholine and cholesterol.
Upton and Buckley (TIBS 20, May 1995 p 178-179) and Brumlik and Buckley (J. of Bacteriology Apr. 1996 p 2060-2064) teach a lipase/acyltransferase from Aeromonas hydrophila which has the ability to carry out acyl transfer to alcohol acceptors in an aqueous media.